Terminal for assembly into a terminal block

ABSTRACT

An improved terminal includes a central portion which is uniformly collapsed by the closure of a terminal board mold. The central portion of the terminal is given convex sides and is pierced by a cylindrical, central opening in such a manner that two uniformly convex columns are formed. Shoulders on either side of the central portion engage the edges of the mold. When the mold closes, the convex columns buckle uniformly and provide an extremely close fit between the shoulders and the mold. Flash from the mold is thus prevented from forming on the exposed portion of the terminal.

United States 3,o,ii

Inventor Norman Deutseh Morton Grove, 1111.

Appl. No. 25,797

Filed Apr. 6, 1970 Patented Dec. 21, 11971 Assignee C. P. Clare & Company Chicago, llll.

TERMINAL FOR ASSEMBLY KNTO A TERMINAL BLOCK 7 Claims, 7 Drawing Figs.

11.8. C1 339/220 llll, 339/276 R int. Cl lli0lllr 9/141 Field of Search 339/220, 276, 198

References Cited UNITED STATES PATENTS 2,755,453 7/1956 Cloutier 339/220 B Primary Examiner-Richard E. Moore Assistant Examiner-Robert A. Hafer Attorney-Mason, l(olehmainen, Rathburn dz Wyss Great Britain 339/220 ABSTRACT: An improved terminal includes a central portion which is uniformly collapsed by the closure of a terminal board mold. The central portion of the terminal is given convex sides and is pierced by a cylindrical, central opening in such a manner that two uniformly convex columns are formed, Shoulders on either side of the central portion engage the edges of the mold. When the mold closes, the convex columns buckle uniformly and provide an extremely close fit between the shoulders and the mold. Flash from the mold is thus prevented from forming on the exposed portion of the terminal.

PATENIED 05021 m 3,629,811

Mom/ml Dsurscfl Arron/5Y5.

TERMINAL FOR ASSEMBLY INTO A TERMIINAIL BLOCK The present invention relates to the manufacture and design of electrical terminals and electrical terminal blocks, and more particularly to the design of terminal block assemblies for miniature relays and the like produced by molding a plurality of terminals into a single terminal block assembly.

In constructing miniature relay assemblies, it is customary to provide a molded terminal block out of which terminals ex tend in two directions. One side of each terminal connects to the winding or contacts of the relay, and the other side connects to external circuitry. The relay is then enclosed in a suitable protective case so as to be maintained in a dust free environment. It is important in the manufacture of such a terminal block that no plastic flash be allowed to form at the junction of the terminals with the terminal block. Such flash can interfere with soldering or welding operations and can break free and contaminate the relay contact surfaces. For this reason, the central portion of such terminals is usually thicker than the extended cantilever portions to which external components and the relay are attached. The central portion engages the two surfaces of the mold when the mold is closed and effectively seals the mold so that flash cannot occur. The surfaces of the central portion which come in contact with the mold are called shoulders.

A major problem in manufacturing terminal blocks of this type is the wear which the terminal shoulders cause to the molds. Because it is impossible to maintain close tolerances in the manufacture of economical terminals, the central portions of all terminals are not necessarily of the same thickness. If flash is to be prevented, the molds must be closed with sufficient force to compress oversized central portions down to the same thickness as undersized central portions so that a good seal is achieved around all the terminals within the mold. See, for example, U.S. Pat. No. 3,210,453. Compressing the central portions in this manner, however, causes excessive mold wear and tear and necessitates frequent mold replacement.

Past attempts to minimize the force which the terminal central portions apply to the mold through change in terminal design have been unsuccessful. Terminals are known which have perforated or notched central portions, but use of such terminals does not substantially reduce the amount of mold wear which occurs. The shoulders of a notched or perforated terminal are still held apart by one or more rigid, straight columns of solid material. These columns cannot be slimmed down to the point where the mold closure force is reduced to an acceptable level without unduly weakening the terminal. Overly slender columns are easily fractured, and fractures of this type can degrade electrical conductivity.

A primary object of the present invention is to provide a terminal which can be easily and uniformly compressed by a relatively low mold closure force.

Another object of the present invention is to design a terminal that is not likely to fracture because of stresses induced by mold closure.

In accordance with these and many other objects, an embodiment of the present invention comprises briefly a terminal having shoulders joined together by two curved columns. The cross-sectional area of each curved column is relatively uniform and is large enough to give the terminal sufficient strength to resist fracture. The curvature of the columns greatly reduces the force which the shoulders exert against the mold, and thus minimizes mold wear. This reduction in force results because a curved column is far easier to compress than is a straight column having the same cross-sectional area. The principle which underlies this decreased force requirement is similar to the principle which underlies Euler's well-known formula for the maximum compressive stress that may be applied to a column.

Other objects and advantages of the present invention are pointed out in the detailed description which follows, and the features of novelty which characterize the present invention are pointed out with particularity in the claims annexed to and forming a part of this specification.

For further understanding of the present invention reference is made to the drawings wherein:

FIG. I is a perspective view of a terminal block constructed in accordance with the principles of the present invention;

FIG. 2 is a perspective view of a terminal used in constructing the terminal block shown in FIG. 1;

FIG. 3 is a perspective view of an alternative form of terminal suitable for use where a terminal block is to be mounted upon a printed circuit block or is to be included in a wire wrap assembly; and

FIGS. 4 to 7 show the method whereby the terminal block shown in FIG. 1 is assembled:

FIG. 4 is a sectional elevational view of a partially closed mold containing the terminal shown in FIG. 2,

FIG. 5 is a sectional plan view taken along the line 5-5 in FIG. 4,

FIG. 6 is a sectional elevational view of a closed mold containing the terminal shown in FIG. 2 and also containing plastic material which forms the terminal block, and

FIG. 7 is a sectional plan view taken along the line 77 in FIG. 6.

Referring now to FIG. 2, there is shown a terminal designed in accordance with the present invention and indicated generally by the reference numeral 111. The terminal 10 includes a central portion 12, a cantilever portion 14 extending in one direction from the central portion 12, and a cantilever portion 16 extending in the opposite direction from the central portion 12. The two cantilever portions 14 and 16 are generally flat and elongated. A hole 18 in the short cantilever portion 14 is provided for the mounting of an electrical contact for a relay. A larger hole 20 in the longer cantilever portion 16 is provided through which wire can be passed so that a solid electrical connection can be made between the portion 16 and external electrical devices. The central portion 12 is generally about twice the thickness of the cantilever portions 14 and 16. Between the cantilever portions 14 and 16 and the central portion 12 are two shoulders, 21 first shoulder 22 adjacent the short cantilever portion 14 and a second shoulder 24 adjacent the longer cantilever portion 16. The shoulders 22 and 24 are perpendicular to the cantilever portions 14 and 16. When the shoulders 22 and 24 are forced into engagement with the edges of a mold, they prevetnt flash from flowing along the cantilever portions 14 and 16.

In accordance with a basic principle of the present invention, the central portion 12 includes a pair of curved columns 26 and 28 each having a relatively uniform cross section. The columns 26 and 28 curve uniformly about a centrally located circular, cylindrical opening 30 in the central portion 12. The outer surfaces 32 and 34 of the curved columns 26 and 28 are cylindrically shaped so as to maintain the cross-sectional uniformity of the convex columns 26 and 28 over a considerable distance. The end portions 36, 38, 40, and 42 of the outer surfaces 32 and 43 curve away from the central opening 30 and bulge outward to form a smooth connections to the shoulders 22 and 24.

FIG. 3 shows a terminal indicated generally as 44 and also designed in accordance with the present invention. The terminal 44 includes cantilever portions 46 and 48 which are thick and narrow rather than thin and. wide. The cantilever portion 48 is designed for wire wrapping rather than for wire soldering, or for printed circuit board use. A central portion 50 of the terminal 44 again includes two curved columns 52 and 54 having uniform cross-sectional areas. These columns 52 and 54 are arched about a centrally located circular, cylindrical opening 56 and include cylindrical outer surfaces 58 and 60 which are curved to keep the cross sections of the columns 52 and S4 uniform over a considerable length of the columns. End portions 62, 64, 66, and 68 of the curved outer surfaces 58 and 60 are curved outwardly from the opening 56 to provide a smooth junction between the columns 52 and 54 and the shoulders 70 and 72 adjacent the cantilever portions 46 and 48. As in the case of the terminal 10, the shoulders 70 and 72 are perpendicular to cantilever portions 46 and 48 and thus form a tightjoint with the edges of a terminal block molding die when the die is closed about the terminal 44.

FIGS. 4 to 7 illustrate how the columns 26 and 28 of the terminal (shown in FIG. 2) behave when a terminal block molding die is closed about the terminal 10. H6. 4 shows the leftand right-hand portions of the molding die 74 and 76 closed about the terminal 10 to the point where inner surfaces 78 and 80 of the die sections 74 and 76 first come into contact with the shoulders 22 and 24 of the terminal 10. A gap 82 exists between the leftand right-hand portions of the die 74 and 76 since the die has not yet'fully closed. FIG. ,5 is a plan view of the terminal 10 within the die sections 74 and 76 showing that the columns 26 and 28 have not yet been buckled by closure of the die sections 74 and 76.

FIGS. 6 and 7 show the same die sections 74 and 76 fully closed about the terminal 10, and also show the terminal block material 84 filling all open spaces between the die sections 74 and 76. H6. 7 shows a plan view of the die sections 74 and 76 sectioned to reveal the terminal 10 within the material 84. The central opening 30 in the terminal 10 is no longer circular but is oval due to the columns 26 and 28 having buckled. The oval central opening 30 and also the curved end portions 36, 38, 40, and 42 are all filled with the material 84, and this prevents both longitudinal and rotational motions of the terminal 10 after the die sections are broken apart. The uniform shape of the columns 26 and 28 causes the columns to buckle uniformly under the force applied to the shoulders 22 and 24 by the inner surfaces 78 and 80 of the die sections 74 and 76. The uniformity of this bending is a basic property of all curved columns subjected to compressive loads. This property ensures that a uniform bend is always produced in the columns and also insures that no fracture of the columns can occur.

The amount of force required to close the die sections 74 and 76 is minimal because of the curvature of the columns 26 and 28. It is well known in the field of engineering mechanics that once a column assumes a curved shape, the column has very little ability to resist further compressive loading. The amount of stress needed to close the die is easily varied by changing the diameter of the central opening 30. If a smaller closing force is required, the central opening 30 is made larger, and if a larger closing force is required, the central opening 30 is made smaller. The shape of the columns 26 and 28 is such that the central opening 30 can be changed in diameter without the necessity of restructuring any other portions of the terminall 0.

While the preferred embodiment of the present invention has been described, it will be understood that numerous modifications and changes will occur to those skilled in the art.-lt is therefore intended to cover all such modifications and changes as fall within the true spirit and scope of the present invention in the appended claims.

What is claimed as new and desired to be secured by letters Patent of the United States is:

l. A terminal for use in the construction of a terminal block comprising:

first and second relatively uniformly curved and relatively uniformly cross-sectioned columns;

first and second members spaced apart from one another and joined by said columns to form a central portion for the terminal;

first and second parallel, outwardly facing shoulders defined by the outwardly facing surfaces of said first and second members and located on opposite sides of said central portion; and at least one cantilever portion attached to one of said shoulders and extending outwardly from said shoulder;

whereby said first and second shoulders may be forced toward each other by forces which cause said first and second columns to become more curved.

cylindrical opening in the central ortion of the terminal.

3. A terminal in accordance Wl h claim 2 wherein the members, when measured in a direction perpendicular to said cantilever portion and to the axis of said cylindrical opening, are wider towards the shoulders than they are adjacent the columns, and wherein the outer surfaces of said central portion are convexly curved to follow the curve of the circular opening over a portion of their lengths and are concavely curved outward over the end portions of their lengths so as to flow uniformly into said first and second members.

4. A terminal in accordance with claim 2 wherein the outer surfaces of said central portion are convexly curved to follow the curve of the circular opening over a portion of their lengths, are approximately parallel to one another towards the end portions of their lengths, and are concave between said convex and parallel portions.

5. A terminal for mounting in a terminal block comprising:

a central portion having planar and parallel upper and lower surfaces; first and second planar, parallel, and oppositely faced shoulders perpendicular to said upper and lower surfaces; a right circular, cylindrical, centrally located opening having an axis which is perpendicular to said upper and lower surfaces; and first and second cylindrical side surfaces all elements of which are perpendicular to said upper and lower surfaces, said side surfaces each having a central, circular, convex portion defining convex columns of uniform cross section about said centrally located opening and each having two peripheral portions curving inwardly towards a perpendicular meeting with said oppositely faced shoulders; and

two cantilever portions extending perpendicularly outwards from said oppositely faced shoulders.

6. A terminal for mounting in a terminal block comprising:

a central portion having planar and parallel upper and lower surfaces; first and second planar, parallel, and oppositely faced shoulders perpendicular to said upper and lower surfaces; a right circular, cylindrical, centrally located opening having an axis which is perpendicular to said upper and lower surfaces; and first and second cylindrical side surfaces all elements of which are perpendicular to said upper and lower surfaces, said side surfaces each having a central, circular, convex portion defining convex columns of uniform cross section about said centrally located opening and each having two peripheral portions curving away from said centrally located opening and respectively connecting to the oppositely faced shoulders; and

two cantilever portions extending perpendicularly outward from said oppositely faced shoulders.

7. A terminal designed for mounting in a terminal block comprising:

first and second members spaced apart from one another;

outwardly, oppositely facing surfaces on the most distant faces of said respective first and second members defining first and second parallel shoulders;

at least one cantilever portion connected to one of said first and second shoulders and extending perpendicularly outward from said shoulder; and

first and second columns connecting said members together, said columns each having a uniform cross section that is varied as needed to smoothly join said columns to said members, and said columns being uniformly curved to minimize the force required to press said shoulders towards one another and to evenly distribute over the length of said columns any such force as might be applied to said shoulders. 

1. A terminal for use in the construction of a terminal block comprising: first and second relatively uniformly curved and relatively uniformly cross-sectioned columns; first and second members spaced apart from one another and joined by said columns to form a central portion for the terminal; first and second parallel, outwardly facing shoulders defined by the outwardly facing surfaces of said first and second members and located on opposite sides of said central portion; and at least one cantilever portion attached to one of said shoulders and extending outwardly from said shoulder; whereby said first and second shoulders may be forced toward each other by forces which cause said first and second columns to become more curved.
 2. A terminal in accordance with claim 1 wherein the opening defined by said columns and said members is a circular, cylindrical opening in the central portion of the terminal.
 3. A terminal in accordance with claim 2 wherein the members, when measured in a direction perpendicular to said cantilever portion and to the axis of said cylindrical opening, are wider towards the shoulders than they are adjacent the columns, and wherein the outer surfaces of said central portion are convexly curved to follow the curve of the circular opening over a portion of their lengths and are concavely curved outward over the end portions of their lengths so as to flow uniformly into said first and second members.
 4. A terminal in accordance with claim 2 wherein the outer surfaces of said central portion are convexly curved to follow the curve of the circular opening over a portion of their lengths, are approximately parallel to one another towards the end portions of their lengths, and are concave between said convex and parallel portions.
 5. A terminal for mounting in a terminal block comprising: a central portion having planar and parallel upper and lower surfaces; first and second planar, parallel, and oppositely faced shoulders perpendicular to said upper and lower surfaces; a right circular, cylindrical, centrally located opening having an axis which is perpendicular to said upper and lower surfaces; and first and second cylindrical side surfaces all elements of which are perpendicular to said upper and lower surfaces, said side surfaces each having a central, circular, convex portion defining convex columns of uniform cross section about said centrally located opening and each having two peripheral portions curving inwardly towards a perpendicular meeting with said oppositely faced shoulders; and two cantilever portions extending perpendicularly outwards from said oppositely faced shoulders.
 6. A terminal for mounting in a terminal block comprising: a central portion having planar and parallel upper and lower surfaces; first and second planar, parallel, and oppositely faced shoulders perpendicular to said upper and lower surfaces; a right circular, cylindrical, centrally located opening having an axis which is perpendicular to said upper and lower surfaces; and first and second cylindrical side surfaces all elements of which are perpendicular to said upper and lower surfaces, said side surfaces each having a central, circular, convex portion defining convex columns of uniform cross section about said centrally located opening and each having two peripheral portioNs curving away from said centrally located opening and respectively connecting to the oppositely faced shoulders; and two cantilever portions extending perpendicularly outward from said oppositely faced shoulders.
 7. A terminal designed for mounting in a terminal block comprising: first and second members spaced apart from one another; outwardly, oppositely facing surfaces on the most distant faces of said respective first and second members defining first and second parallel shoulders; at least one cantilever portion connected to one of said first and second shoulders and extending perpendicularly outward from said shoulder; and first and second columns connecting said members together, said columns each having a uniform cross section that is varied as needed to smoothly join said columns to said members, and said columns being uniformly curved to minimize the force required to press said shoulders towards one another and to evenly distribute over the length of said columns any such force as might be applied to said shoulders. 